This invention relate to forming reflective pavement marking article with multiple, precise raised reflective faces which monolithically including micro cube corner reflective elements within defined cell like areas.
Unitary raised reflective pavement marking have been extensively used to direct roadway traffics by retro reflecting incident lights to incoming automobiles.
This type of reflective marking usually augmented either by several non-reflective markers, intermittent paint strips or sheets of polymeric stripping.
Varieties of raised reflective marking products are readily available for use directly on roadway, thereby complimenting paint striping or other raised non-reflective markers.
Alternatively, various sheet marking have been developed as an alternative composition for such long, intermittent lane marking for roadway.
Several methods of making reflective sheeting for such pavement marking have been developed. Such previous arts include multiple raised portions with retro-reflectivity.
As an example, U.S. Pat. No. 6,303,058 B1 to Kelley et al that uses a top, preformed reflective sheet with pre-embossed cube corner reflective elements.
This sheeting comprised of multiple, preformed and bonded laminate that needs to be bend into multiple raised portions without any integrally formed load carrying walls, then applying a filling material into the cavities to provide the structural support needed and to retain the raised reflective faces in position.
Other available arts of making reflective sheets with multiple, raised reflective regions are the type that embed optical elements, such as preformed spherical beads, into a binder resinous layer, as in U.S. Pat. No. 6,326,053 B1 assigned to 3M innovative Property Company. Various arts of forming or embossing cube corner elements on either specific length of plastic articles or on continuous sheeting are available; U.S. Pat. No. 3,712,706 to Stamm, which is incorporated herein by this reference, explains in detail the method of forming such reflective sheeting. Also referenced herein are U.S. Pat. No. 3,873,184 to Heenan et al; U.S. Pat. Nos. 3,684,348, 3,689,346, 3,810,804 and 4,244,683 to Rowland and U.S. Pat. No. 4,025,159.
The object of this invention is to provide a novel method of integrally forming a by-directional partition and load carrying walls in support of each two opposing, raised reflective faces within a reflective sheeting, thereby eliminating the need for back-filling these protruded cavities with resinous material for structural support.
It is further objective of this invention is to provide a method of manufacturing reflective sheeting having multiple, raised reflective faces in relatively inexpensive and with uniform dimension.
The incorporation of monolithically formed load carrying structural walls defining multiple cube corner elements within cell like areas has been explained in detail in U.S. Pat. No. 6,334,734 and application Ser. No. 09/982,044 belonging to this applicant, which are incorporated herein by this reference.
The present invention relates to improved pavement marking having low profiled reflective faces with multiple of integrally formed strippings.
The present invention also includes an efficient method of fabricating the reflective pavement marker.
The reflective faces as well as the integrally connected stripping portions incorporate multiple of micro-prismatic cube corner reflective elements within the internal surfaces of the cell like areas. The cell like areas are defined by a multi directional or by directional load carrying partition walls depending on the size and height of the reflective faces being incorporated.
Several methods are available for manufacturing the present invention.
A continuous method of production would include a compression molding techniques.
This method comprises of a continuously fed, optically transparent sheet which pass through cavity pre-forming station under sufficient vacuum or pressure to pre-form a contoured surface nearly the shape of the cavities of the compression molding die.
This top transparent continuously fed sheet can be made of acrylic, polycarbonate or other transparent and ultra violet stable resin of good optical transparency. This transparent sheet can also be pre coated with abrasion resistance hard carbon, silicone dioxide or aluminum trioxide film, utilizing reactive sputtering or chemical vapor deposition methods.
Then a resin dispensing station would inject a transparent, resinous fill material.
The pre-calendared, filled surface then move to a compression molding station having a core segment that simultaneously imprint both, the cube corner reflective elements as well as the load carrying partition walls monolithically on top of said transparent sheet then cure the composite marker.
A compatible sealing sheet would be laid at the base area of the composite marking article, then welding to said base region to form the final reflective pavement marker.
A conveyerized rotational means can continuously move the cavity portion of the compression die, thereby strip release the finished pavement marker onto the next station of cutting and packing.
The production method may include several in between substation such as vibrating the fill surface to eliminate air bubbles, heat, air or cooling water supplies or trimming equipments, as needed.
The raised reflective pavement marker of the present invention includes several advantages over other sheet type or single reflective pavement markers.
This type of reflective marking are suited for replacing the combined pavement lane stripping as well as the raised reflective markers used with such lane stripping. It also can be used as pavement signs and directional markings.
Additionally, this type of retro-reflective marking can be very effective for pedestrian crossing, especially during intensive rain.
This type of sheeting can also find used on vertical objects such as truck trailers, vertical posts, embankments, side curbs, delineators, etc.